|Main author|No. of patients|Duration of follow-up years|Linearized rate of infection|Actuarial freedom from infective endocarditis|
|---|---|---|---|---|
|Pavie|675|5||98.2% for all patients, 97.8% for aortic, 99% for mitral, 100% for multiple valve replacements|
|Duncan (A)|2720|6||97.3% for all patients, 97.4% for aortic valves, 97.6% for mitral valves, 96.3% for multiple valve replacement|
|Ionescu (B)|1171|10||93.7% for all patients, 94.7% for aortic valves, 97.1% for mitral valves, 89.3% for multiple valve replacement|
|Zhu|520|10||98% for all patients|
|Revuelta|239|8|0.67% per patient year||
|Garcia-Bengochea|248|8|0.78% per patient year||
|Holden (C)|290|6|1.1% per patient year||
|Bachet (D)|224|6|1.6% per patient year||

Question: how many looked at more than 500 patients?
Answer: 4